As a method of moving a robot by a manual input operation, a jog-feeding method and a lead-through method are well known. The jog-feeding method is normally performed by operating a moving direction designating member of a robot, such as a jog key or a joy stick on a teaching operation panel.
The jog-feeding provides a convenient method for moving a robot for a desired time period by continuing or discontinuing the operation of the moving direction designating member. The conventional jog feed, however, has restrictions in designating the moving direction. That is, the conventional jog-feeding can designate the moving direction of the robot only along each coordinate axis of a chosen coordinate system (a world coordinate system, a user coordinate system, a tool coordinate system, etc.) (+X, -X, +Y, -Y, +Z, -Z) or around each coordinate axis thereof (+W, -W, +P, -P, +R, -R), and along each of designated robot axes (+J1, -J1, +J2, -J2, . . . ).
Because of those restrictions, a tedious operation is needed such as selectively depressing different jog keys many times to make the robot gradually approach and reach a desired target position, unless the desired target position is on a coordinate axis. In addition, since a moving direction of a robot is designated in the indirect manner, it is difficult for an operator to intuitively know the actual moving direction, making the method inconvenient in this aspect.
The lead-through method uses a force sensor attached to a hand of a robot and a lead-through switch. In this method, when an operator applies an external force to make the hand proceed in a desired direction while depressing the lead-through switch, the force sensor detects the direction of the applied external force and transmits the detected direction to a robot controller to make the robot move in the direction of the external force. This method has an advantage in that a moving direction of the robot is designated in a direct manner, it is easy for an operator to recognize the actual moving direction.
However, this method has a significant problem that the operator needs to stand close to the hand of the robot. Thus, if an erroneous operation or a malfunction should happen when the operator stands close to a robot in order to start the lead-through operation or before standing off the robot after finishing the operation, it may bring serious jeopardy to the operator standing close to the hand of the robot.